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In the Desert
Learning Objective: To find out about desert formations.
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We are going to look at some photos of deserts around the world to see what features we can see.
For each photo, talk about what you can see and how you think each feature
came to be there.
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The Empty Quarter, United Arab Emirates
These diagrams show some of the ways in which sand dunes can form.
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One of the most recognisable features of sandy deserts are sand dunes. Dunes are formed when the wind moves sand particles to form mounds. There are several different types of sand dune which create
patterns, depending on the speed and direction of the wind.
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Only around 20% of all the deserts in the world
are made up of sand. The rest are rocky or
gravelly. In rocky deserts, there are often amazing rock formations
like these.
These rock formations are caused by the effects of temperature, wind and flash floods. Rain does not happen often in deserts but when it does it often causes flash floods. These cause rocks and boulders to be carried along by the water, scraping at the rocks as it travels. This causes the rock to wear
away through a process called erosion.
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A natural arch
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Desert winds also cause erosion. The wind picks up dust and sand which rubs against the rocks as it passes. Over millions of years,
this wears away the rock to create interesting shapes and formations.
This is a picture of a mushroom rock in Egypt. The bottom part of the rock has been eroded, leaving it top heavy.
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A mushroom rock
This rock bridge was formed millions of years ago by a river that has
long since dried up. www.planbee.com
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These natural pillars have formed in the
Sahara desert.
Natural pillars
Natural rock bridge
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These flat-topped mountains are called mesas. They are formed when the land around them is eroded away by wind and water.
Mesa means table in Spanish!
This is the Painted Desert in Arizona, USA. Layers of sand, shale and ancient clay have been revealed through erosion,
showing beautiful coloured rocks. www.planbee.com
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This might look like snow but it is actually a salt basin in the Atacama
desert!
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Another interesting feature of deserts are salt basins. These are formed when water evaporates and leaves the salt that was in the water behind. Salt basins can also be called salt flats or salt plains.
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Have you ever seen a salt basin?
Have you ever seen rock formations like those in the deserts we have
seen today?
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What do you think the most impressive desert
formation is? Why?
Plenary:
